1. Field of the Invention
The present invention relates to a paint supply technology for supplying paint to an application part which applies the paint on an object to be coated (hereinafter, referred to as a “coated object”).
2. Related Art
When coating a coated object, an application part provided on a leading end of an arm of industrial robot sprays paint on the coated object and the paint thus sprayed is applied on the coated object.
Patent Document 1 (JP-A-63-175662) discloses a system for performing the coating on a coated object by an atomizing application part provided on a leading end of an arm of multi-articulated robot. The arm of the multi-articulated robot is provided with a reservoir (hereinafter, referred to as a “cylinder device”) connected to the application part and the paint is supplied from the cylinder device to the application part. When the coating process is completed, the robot makes the cylinder device connected to a paint supply pipe which is provided in a wall of a coating room. In this way, new paint is supplied from the paint supply pipe to the cylinder device.
Patent Document 2 (JP-A-2000-176333) discloses a system in which an application part of a rotary atomizing head type is supported on a leading end of an arm of multi-articulated coating robot to spray paint on a coated object and the paint thus sprayed is applied on the coated object. In this system, a cartridge previously filled with paint is mounted on an application part and the paint is supplied from the cartridge to the application part during application. For this reason, a cartridge exchange device for storing a plurality of cartridges is provided in a coating room.
In the system disclosed in Patent Document 2, paint is supplied by a circulation pressure after the cylinder device is connected to the paint supply pipe. In this case, in order to prevent air from entering the cylinder device, the supply capacity (for example, supply rate) of paint is suppressed low and thus it takes a long time to supply paint.
Meanwhile, in the system disclosed in Patent Document 2, by exchanging the cartridge, paint can be supplied without taking a long time. However, the cartridge exchange device occupying a large space should be provided adjacent to the robot and therefore an increase in size of coating equipment is caused.
Patent Document 3 (JP-U-04-087755) and Patent Document 4 (JP-A-2004-275977) disclose a paint supply system in which a supply valve part (color change valve; hereinafter, referred to as “CCV”) for selectively supplying a plurality of is kinds of paint or cleaning fluid (liquid or gas used in cleaning) is provided. In this system, the cleaning of paint previously used (applied) is performed, during the color change of paint.
According to the configuration of Patent Document 3, during the color change of paint, cleaning liquid (or cleaning air) is supplied from a predetermined valve included in the CCV and thus the interior of the paint supply system (electrostatic coating device) is cleaned. Specifically, the cleaning liquid supplied from the valve passes through the interior of the paint coating system in sequence of the CCV, the paint supply pipe, a cylinder (cylindrical body) of a pump and an electrostatic coating machine (application part). In this way, the paint remaining in each component can be cleaned.
Similarly, according to Patent Document 4, during the color change of paint, the cleaning liquid supplied from a cleaning valve cleans the CCV, a pipe line, a cylinder and a pumping path under a driving influence of the CCV (color change valve mechanism).
However, in a configuration for performing the cleaning of the coating device by supplying the cleaning liquid from the supply valve part (CCV) during the color change of paint, as disclosed in Patent Documents 3 and 4, the cleaning is performed in a state where a relatively large amount of unused paint remains in the components (for example, pipes to supply paint) constituting the coating supply system. As a result, a paint loss (paint to be discarded by cleaning) increases and thus a coating cost required for coating of the coated object increases.